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By Daniel Fischer Every page present in Europe & the U.S.!
| Ahead | Awards 
The latest issue!
| A German companion - only available here! Current mission news: MGS (latest pictures!) + Cassini + Stardust |
When comet Kudo-Fujikawa came close to the Sun in late January, it didn't become really impressive - but comet NEAT may or may not in the 3rd week of February: SOHO's current images, on C/2002 V1 (NEAT) SC, CCNet (item 6) and FG Kometen analysis and of C/2002 X5 (K-F) a SOHO Pick of the Week, S&T, APOD, SC, the view on Jan. 28, the orbit in 3D and an FGK analysis.
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Columbia investigation limps along with no hot leadsLarge fragment of one wing found / long-range image inconclusive / "final" report within 60 days?One week after the Columbia tragedy, more potentially important debris has been found and additional high-resolution images of the orbiter during reentry have surfaced, but no leading theory on the accident has emerged so far. Still the charter of the investigation board has been revised with the specification that a final written report should be produced within 60 days, in a time far shorter than during a typical airliner crash study. Here then are the latest discoveries:
Columbia mystery still wide open - launch incident not the causeContrary to many media reports earlier this week, the investigation is anything but over, and the now-famous launch incident with the piece of insulating foam breaking off the external tank and hitting the orbiter was in all likelyhood not the cause of the disaster on Feb. 1. The fragment just was not heavy enough to cause severe damage to the wing or its heat tiles - and there are actual long-range photographs of the wing underside before and after the foam hit, showing no difference in appearance whatsoever. This, plus extensive analysis of the incident itself (see below), have led shuttle program manager Ron Dittemore to the conclusion: »Right now it just does not make sense to us that a piece of debris would be the root cause for the loss of Columbia and its crew. There's got to be another reason.«There had been speculation that the foam fragment might have contained ice and was therefore much heavier than the assumed 1.2 kg - but ice is now thought to be an unlikely factor as the weather was not cold enough and the ice team did a very thorough search before launch. NASA's working hypothesis is now that something else hit the orbiter at an unknown time between launch and reentry, damaging it so that it started to disintegrate on first contact with the atmosphere. It could even have been space debris or a meteoroid. In any case there are now amateur video tapes available of Columbia's flight over California and Arizona that already show bright objects coming off the orbiter now and then - and there are (yet unconfirmed) reports of small debris having been found in CA, AZ and NM (while more and more big fragments have been found in TX). |
And so the detective work is continuing at full steam, 24 hours a
day, hunting for at least one crucial »missing link« in
the chain of fatal events. As made clear by Dittemore and others
during further news briefings from Feb. 2 to 5,
For example, we know now in detail how NASA handled the launch incident (even the internal protocols have been made available): It was discovered on Jan. 17, the day after launch, studied for days and reported to the mission management on Jan. 24 and 27. Near the forward bipod - where the orbiter is mounted to the ET - a foam fragment of 50 x 40 x 15 cm with a mass of 1.2 kg had broken off and struck the underside of Columbia and the left wing at a very glancing angle (10 to 16°), shattering into a cloud of particles in the process. The size parameters were derived from a hi-res movie and calibrated with photographs of a similar incident during the launch of STS- 112 where the hole in the ET insulation had actually been photographed by the astronauts. Using a computer model known to overpredict damage from impacts, two worst case outcomes of the impact had then been identified: The foam fragment could either have knocked out a single heat tile completely or damaged a number of them partially, over a zone of 80 x 18 x 5 cm. In both cases localized heating would have occurred, causing modest structural damage - but nothing sufficient to cause the disaster or even to affect the flying quality of the vehicle. Consequently there was no cause for alarm, though the incident was discussed with the media on Jan. 31. »We have no concerns whatsoever,« entry flight director Leroy Cain had said at that time: »All of the analysis says that we have plenty of margin« and that the impact could not have been »significant enough to take out any significant amount of tile.« And remember that orbiters have returned safely in the past with entire tiles missing. Even if there had been serious concern, nothing could have been done. Contrary what some pundits (including former astronauts!) have told various media, the STS-107 astronauts had no possibility to conduct an unscheduled EVA to inspect the belly of the orbiter for any damage. And even if they had, they could have done nothing to replace damaged heat tiles as each one has an individual shape. In-orbit repairs are also unheard of. There is also no leeway in changing the entry trajectory to reduce the heat load on one wing (because then the other one would get too hot or the orbiter would not slow down enough - the crew would have had to bail out in mid-flight). And an escape to the ISS was precluded by the different orbital inclination alone. So far nothing indicates that NASA deliberately ignored a serious safety issue here, and even the decision not to try to determine any damage telescopically (whether that worked in earlier cases is a matter of debate) seemed prudent at the time.
No »smoking gun« yet in space shuttle disasterRole of ET foam incident during launch unclear / Columbia flew perfect trajectory right until loss of contact / Crucial clues may be in widely scattered debrisAlmost to the day 17 years after the Challenger disaster NASA has again lost a space shuttle orbiter and its seven-member crew - and as on Jan. 28, 1986, there were only tons of questions but no clear answers on the day of the tragedy, Feb. 1, 2003. As discussed in great detail by grief-stricken NASA managers during a news conference later that day, Columbia had followed the planned reentry trajectory perfectly and apparently also in the planned attitude right until all communication with the orbiter was suddenly lost at 13:59 UTC, 17 minutes before the planned touchdown at the Kennedy Space Center in Florida. At that time Columbia was travelling with Mach 18.3 (5.6 km/s) at an altitude of 63 km, experiencing the greatest heat load of the reentry.The only anomalies noted by mission control in the minutes before were failures of several temperature and pressure sensors in the left side of Columbia that began at 13:53 and multiplied in the following minutes. While such a clustering of malfunctions in independent sensors was unusual, it was no cause for alarm, especially since the astronauts confirmed verbally that from their point of view all was well with the orbiter - and it was during that statement that all communications with Columbia were lost, including telemetry and tracking. »[We] began to know we had a bay day,« chief flight director Milt Heflin recalled: Mission control knew no longer where the orbiter was and what was happening to it. But numerous spectators - and TV crews - in Texas and surrounding states did: They saw Columbia first as the well-known bright star with a long plasma trail (not contrail as said in many reports) - and then suddenly splitting into a shower of bright dots with individual trails. The »ominous« picture (as CNN put it minutes later) was all too familiar: Such had looked the reentry of the Mir space station two years ago (see Update # 221). The visual drama was accompanied by loud noises - and soon thereafter a rain of debris with fragments typically one meter in size or (much) less started to fall onto the rural area. By that time a prepared emergency protocol at NASA - that all had hoped would never be needed - was already in effect. While rescue operations were clearly hopeless this time, the recovery of the debris was the order of the day (involving a host of U.S. agencies) - as was the impounding of all available data, documents and even hardware (used to prepare Columbia for the ill-fated mission STS-107). Several investigation committees are already at work combing through the material, both by NASA and by independent experts. As there may be not much telling evidence in the telemetry, except for the chain of sensor failures, much hope is centering on the physical evidence (even though it is severely damaged and there is no impact-hardened flight data recorder like in an aircraft). And NASA refrains from engaging in any speculations about the root cause of the accident. For example, an incident during the launch of Columbia on Jan. 16 may or may not have something to do with the loss during reentry. A piece of foam had broken off the insulating layer of the External Tank and struck the leading surface of the left wing. After reviewing a high-resolution movie for a »goodly amount of time« (shuttle program manager Ron Dittemore), the incident was concluded to be insignificant. It is raising some eyebrows, though, that the series of sensor failures also affected the left wing of Columbia, albeit starting on its trailing side. Late on Feb. 1st there was also talk about unusual movements of the elevons on Columbia's wings, just before the orbiter was lost. For the time being all shuttle launches are suspended. The ISS is not immediately affected by that as there are supplies on board lasting until June - and there is always the Soyuz »taxi« to get off the station if need be. (Based largely on two NASA news conferences on Feb. 1 and several CNN special programs on Feb. 2) |
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Artemis finally reaches operational orbitEighteen months after an Ariane 5 had delivered it into an orbit that was way too low (see Update # 226 story 4), ESA's experimental communications satellite Artemis has finally reached the geostationary orbit - by using its ionic propulsion service in a way it had never been designed for. Initially provided on an experimental basis to correct orbit drift once Artemis was on station, the ion thrusters were used to raise the satellite's orbit from 31,000 km to 36,000 km. This is a much slower process than using a conventional apogee boost motor - a bit like using an outboard motor to drive an ocean liner - but here it was a case of better late than never! Before the orbit-raising operations could get underway, a huge reprogramming effort was required and it even proved necessary to develop completely new software from scratch, against the clock.Those operations began with an initial, rapid shift to a safe parking orbit beyond the upper Van Allen Radiation Belt, the required thrust coming from the satellite's conventional, chemical-powered apogee boost motors. The small ionic motors then took over in February 2002 and, at an average of 15 kilometres a day, Artemis rose in spirals towards geostationary orbit - needless to say, there were incidents and unexpected problems on the way. In the final approach phase the chemical motor fired thrice in succession to adjust the satellite's velocity. Artemis has now taken up its operational station in Earth orbit and its instruments, placed in hibernation throughout the recovery campaign, have been reactivated. Once all systems are fully active Artemis will be ready to embark on what may prove to be a ten-year operational career, barely less than the service life that had been planned before these celestial gymnastics became necessary. |
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SORCE launched, will continue measurements of solar irradianceThe Solar Radiation and Climate Experiment (SORCE) was safely delivered into Earth orbit on Jan. 25, carried by a winged Pegasus XL rocket air-dropped over the Atlantic Ocean east of Florida. The $122m mission will help scientists understand the Sun's role in climate change here on Earth by measuring the amount of solar energy reaching the planet as our nearest star radiates through its various cycles. SORCE, with a mass of just 287 kg, carries four instruments: a Total Irradiance Monitor (TIM), the Spectral Irradiance Monitor (SIM), Solar Stellar Irradiance Comparison Experiment (SOLSTICE) and the Extreme Ultraviolet Photometer System (XPS). The TIM, SIM and SOLSTICE will measure solar irradiance and the solar spectrum, while the XPS detects high-energy radiation from the Sun. |
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All other historical issues can be found in the Archive.
The U.S. site of this Cosmic Mirror has been visited
since it was issued (the German site has no counter).
Compiled and written by Daniel Fischer
(send me a mail to dfischer@astro.uni-bonn.de!), Skyweek